Function syntax
===============

Solve the following exercises manually. Then, use a Python shell to
check your answers.

#. The authors of the following functions claim that all of them return the double of a given value. Justify which of them are correct and which are not.

   .. code:: python

       def double_1(a):
          b = 2*a

       def double_2(a):
          a = 2*a
          return a

       def double_3(a):
          return 2*a

       def double_4(a):
          a = 3
          return 2*a

#. Which is the result of the call ``f('2', 2)`` ? And the call
   ``f('99', '100')``. And which is the type of these results ?

   .. code:: python

       def f(a, b):
          return a>b

#. Which is the result of the call ``g(3, 2)`` ? 

   .. code:: python

       def g(a, b):
          a = subtract(b, a)
          b = product(a, b)
          return b, a

       def subtract(m, n):
          return m-n

       def product(m, n):
          return m*n

#. What does the following function return for the following calls ?:
   ``multiple(10, 2)``, ``multiple(10,3)``, ``multiple(10, 4)`` and
   ``multiple(10, 5)``.

   .. code:: python

    def multiple(num, x):
        return num%x ==0